L'electrophorese sur gel d'amidon constitue une methode puissante et economiquement abordable pour estimer la variabilite genetique des especes vegetales de leurs populations. Les loci d'alloenzymes representent caracteres typiquement monogeniques, qui se recombinent facon independante affichent alleles co-dominants. Des tailles d'echantillon variant 30-50 individus analyses 10-20 polymorphes s'averent suffisantes caracteriser adequate diversite d'une population evaluer comment repartit...

This study documents the scale and intensity of drying over last half century in Kenai Lowlands south-central Alaska. Using historical aerial photos field sampling wetlands, including muskegs, kettle ponds, closed open basin lakes, we present data on successional changes woody vegetation between 1950 1996. The results this suggest that Peninsula is becoming both woodier its drier. A regional analysis 1113 random points indicated increased forest cover decreased wet areas burned unburned...

We document accelerating invasion of woody vegetation into wetlands on the western Kenai Peninsula lowlands. Historical aerial photography for 11 wetland sites showed that herbaceous area shrank 6.2%/decade from 1951 to 1968, and 11.1%/decade 1968 1996. Corresponding rates converting shrubland were 11.5% 13.7%/decade, respectively, and, nonforest forest, 7.8% 8.3%/decade, respectively. Black spruce ( Picea mariana (Mill.) BSP) forests three perimeters established since Little Ice Age...

Increasing temperatures have resulted in reduced growth and increased tree mortality across large areas of western North American forests. We use tree-ring isotope chronologies (δ13 C δ18 O) from live dead trees four locations south-central Alaska, USA, to test whether white spruce killed by recent beetle (Dendroctonus rufipennis Kirby) outbreaks showed evidence drought stress prior death. Trees that were more sensitive spring/summer temperature and/or precipitation than survived. At two our...

Theoretical models and computer simulations of the genetic structure a continuous population predict existence patches highly inbred individuals when gene flow within is limited. A map three genotypes two-allele locus expected to exhibit homozygotes embedded in matrix heterozygotes, search for such patch was made on 160 × m plot 60+ ha old-growth stand Quercus laevis (turkey oak). Approximately 3400 trees were genotyped 9 polymorphic loci using starch-gel electrophoresis, analyzed with...

We used tree ring data (AD 1601-2007) to examine the occurrence of and climatic influences on spruce beetle (Dendroctonus rufipennis) outbreaks in south-central southwest Alaska found evidence regional-scale dating from mid-1700s, related climate variability at multiple temporal scales. Over interannual time scales (approximately 1-3 years), El Niño years, combined with severe late-summer drought, appeared contribute significantly study area. multidecadal (up approximately 40 cool-phase...

Quercus laevis Walt, (turkey oak) and Q. margaretta Ashe (scrubby post are important scrub oaks in the sandhills forest communities of Coastal Plain southeastern United States. We used allozyme loci Ripley's L‐statistics to examine clonal structure spatial dispersion these species. greater than 1.5 m height were randomly dispersed on a scale 0–40 m; smaller individuals (< m) slightly clustered 0–12 m. Larger separated by ≤1 had 15% probability being ramets same clone. showed strong...

The complex response of the forest‐tundra ecotone (FT) to climate change may not generalize well geographically. We document FT changes in a nonpermafrost region southcentral Alaska during known warming period. Using 1951 and 1996 orthophotos overlain on digital elevation models across 800 km 2 west Kenai Mountains, we identified cover classes topography for 978 random points highest closed‐canopy conifer patches along 205 altitudinal gradients. Results show 29% area increased woodiness,...

Abstract. Permafrost presence is determined by a complex interaction of climatic, topographic, and ecological conditions operating over long time scales. In particular, vegetation organic layer characteristics may act to protect permafrost in regions with mean annual air temperature (MAAT) above 0 °C. this study, we document the residual plateaus western Kenai Peninsula lowlands south-central Alaska, region MAAT 1.5 ± 1 °C (1981–2010). Continuous ground measurements between 16 September 2012...

Several studies have noted a relationship between vegetation type and fire frequency, yet despite the importance of ecosystem processes such as long-term relationships disturbance, climate are incompletely understood. We analysed pollen, plant macrofossils sedimentary charcoal from three lakes within Kenai lowlands to determine postglacial for Boreal forest southwest Alaska. An herb tundra was established in following deglaciation by 13 000 cal. BP. Salix, Alnus probably Betula kenaica,...

Xylem (water) pressure potential was measured through one winter in evergreen black spruce (Piceamariana (Mill.) B.S.P.) and deciduous larch (Larixlaricina (Du Roi) K. Koch) Fairbanks, Alaska. Larch values averaged about −1.0 MPa, with occasional dips to −1.5 MPa. Black showed similar until May, when dropped −2.5 Regression models indicate that desiccation of responds primarily cumulative vapor deficit (drought), which becomes severe as spring daylight rapidly increases (R 2 = 80%). In...

Male euglossine bees, including Euglossa and Eulaema, collect fragrances from flowers other sources probably biochemically modify the release them to attract females for mating. The fragrance-collecting activity follows a diel cycle that may be influenced by variation in thermal environment. To ascertain degree of influence environment on these tropical we used carcasses as temperature sensors measure operative environmental temperatures (TF) bees forest openings (full sunlight) understory...

ABSTRACT Boreal wetlands hold vast stocks of soil carbon (C), which may be vulnerable to changes in climate. In southcentral Alaska, the Kenai Lowlands have experienced a warming and drying trend that has led woody vegetation encroachment into herbaceous wetlands. We examined whether predicted higher rates gross ecosystem photosynthesis (GEP) would offset by respiration (ER) wetland communities. measured net exchange (NEE) four communities along hydrologic gradient during (1) warm dry...

Several important North American coastal conifers – having immigrated during the Holocene from southeast reach their northern and upper elevation limits in south-central Alaska. However, our understanding of specific timing migration has been incomplete. Here, we use two new pollen profiles a high-elevation site Eastern Kenai Peninsula–Prince William Sound region, along with other published records, to investigate biogeography development history modern Picea (spruce)– Tsuga (hemlock)...

Quercuslaevis Walt, (turkey oak) is a dominant hardwood tree in the sandhills communities of coastal plain southeastern United States. Estimates allozyme diversity for this species were typical oaks (H es = 0.184) and within eleven populations was also relatively high ep 0.178). Genetic among low (G ST 0.032), being about one third mean other oak species. We interpret interpopulation homogeneity as relict previously more continuous distribution longleaf pine (Pinus palustris Mill.)–turkey...